Without limiting the scope of the present invention, its background will be described in relation to forming a window in a casing string for a multilateral well, as an example.
In multilateral wells it is common practice to drill a branch or lateral wellbore extending laterally from an intersection with a main or parent wellbore. Typically, once the casing string is installed and the parent wellbore has been completed, a whipstock is positioned in the casing string at the desired intersection and then one or more mills are deflected laterally off of the whipstock to form a window through the casing sidewall.
In certain installations, it is desirable to drill the lateral wellbore in a predetermined direction from the parent wellbore such as out of the high side of the parent wellbore. In such installations, it is necessary to form the window at a predetermined circumferential orientation relative to the parent casing. In order to properly position and rotationally orient the whipstock such that the window is milled in the desired direction, a latch assembly associated with the whipstock is anchored into and rotationally oriented within a latch coupling interconnected in the casing string. The latch assembly typically includes a plurality of spring operated keys, each of which have an anchoring and orienting profile that is received in a mating profile formed internally within the latch coupling. In this manner, when the latch assembly is operatively engaged with the internal profile of the latch coupling, the latch assembly and the equipment associate therewith may be anchored and rotationally oriented in the desired direction within the casing string.
It has been found, however, that operative engagement of the latch assembly with the latch coupling sometimes fails. For example, a latch coupling may be damaged during completion of the parent wellbore. Alternatively or additionally, drilling fluid solids or other debris may obstruct portions of the internal profile of the latch coupling such that it fails to properly interact with the latch assembly. In such situations, numerous additional trips into the well may be required to perform remedial action including, for example, installation of a new position reference device that is suspending within the casing via a packer assembly.
Accordingly, a need has arisen for improved system for constructing an exit for a multilateral well that does not require numerous additional trips into the well in the event of a latch coupling failure. In addition, a need has arisen for such an improved system that does not require remedial action to be performed in the event of a latch coupling failure. Further, a need has arisen for such an improved system that does not require installation of a new position reference device in the casing string in the event of a latch coupling failure.